In portable circular saws, it is frequently desired to make tool adjustments for controlling particular aspects of a cut. For example, it is known to provide a portable circular saw with a mechanism for adjusting a depth of cut by controlling the extent to which a blade portion emerges below a base or shoe which supports the saw on a workpiece. One example of a portable circular saw constructed to include a depth of cut adjustment mechanism is shown and described in commonly assigned U.S. Pat. No. 4,982,501, which is hereby incorporated by reference as if fully set forth herein.
U.S. Pat. No. 4,982,501 discloses a portable circular saw including a depth of cut adjustment mechanism which is effected by pivoting movement between the shoe and a motoring gear case housing about a pivot connection rearward of the motor and gear case housing. Forward of the housing, an upwardly extending arcuate depth slide is fixed to the shoe. The depth slide slidably engages an arcuate depth guide carried by the motor and gear case housing. Towards the upper end of the depth slide and in generally fixed relationship to it, a clamping assembly selectively clamps the depth slide and depth guide together to establish a depth of cut adjustment setting.
It is also known to provide a portable circular saw with a bevel angle adjustment mechanism for adjusting a bevel angle of cut. One example of such a circular saw is shown and described in U.S. Pat. No. 5,452,515, which is hereby incorporated by reference. The circular saw shown in U.S. Pat. No. 5,452,515 includes a base plate, a saw blade arranged so that a bevel angle is adjustable relative to the base plate, a clamping block supported by the base plate and provided with a turning guide slot, a clamping screw extending through the turning guide slot, and supporting arm. The clamping block has a plurality of arresting pockets arranged along the turning guide slot. The clamping screw carries at least one axially spring-biased displaceable arresting sleeve which is arrestingly positionable in a respective one of the arresting pockets.
A desirable bevel angle adjustment mechanism provides for convenient, easy and speedy manipulation to set the desired bevel angle. In some applications, an operator may need to change the bevel angle setting very frequently so that an apparently minor adverse characteristic of the adjustment procedure may, in the long run, make a significant difference in operating efficiency and cost. Two significant aspects of a bevel angle adjustment mechanism are first, the ease of effecting relative movements between portions of the adjustment mechanism, and second, the accuracy and ability to set desired bevel angles.
Prior known arrangements for adjusting a saw blade relative to a base or shoe for adjusting a bevel angle of cut, including but not limited to U.S. Pat. No. 5,452,515, may operate to positively locate a saw blade relative to a base or shoe at one or more predetermined bevel angles. However, such prior known arrangements are not without their drawbacks. For example, many known arrangements are awkward to use because the user must remove and hold a lock and simultaneously adjust the saw to a desired bevel angle setting. In addition, many known arrangements cannot be offset slightly from common detented angles. For example, the arrangement disclosed by U.S. Pat. No. 5,452,515 includes a plunger which locks in a recess. If the adjustment is set slightly off from a common angle, the plunger tends to reset in the recess for the common angle. Accordingly, slight variations with such an arrangement are not possible.
The present invention comprises an improvement over prior known circular saw bevel angle adjusting systems, including those disclosed in the aforementioned patents.
In the preferred embodiment, the bevel angle adjustment mechanism of the present invention includes a mounting bracket fixed to a gear case housing of the saw and a quadrant bracket carried by the shoe. The mounting bracket is pivotally attached to the quadrant bracket to permit the shoe to be adjusted relative to the remainder of the saw and thereby adjust the bevel angle of the blade relative the shoe. A bolt is axially and nonrotatably fixed in the mounting bracket and extends through a slot in the quadrant bracket. A lever is fixed to the nut and is rotatable with the nut to clamp and unclamp the quadrant bracket relative to the mounting bracket by tightening and loosening the nut on the bolt. A selected bevel angle is indicated by an indicator extending from the mounting bracket and by a scale extending along the slot in the quadrant bracket. The adjustment mechanism has a ball detent to indicate or provide a stop for bevel angle settings (e.g. 221/2.degree. and 45.degree. ) that are commonly used for cutting. The detent is formed by a ball (supported in the bracket) which cooperates with a series of recesses formed in a forward surface of the mounting bracket. The ball is supported in a hollow cylindrical bushing press fit into an aperture of the quadrant bracket and is spring biased toward the mounting bracket by a spring. The detent selectively cooperates with the recesses to positively define a plurality of predetermined bevel angle settings.
In one form, the present invention provides a circular saw including a housing subassembly having a motor and a circular saw blade rotatably driven by the motor. The circular saw further includes a base and a bevel angle adjustment mechanism. The bevel angle adjustment mechanism pivotally interconnects the base to the housing such that the circular saw blade is adjustable relative to the base through a range of bevel angles. The bevel angle adjustment mechanism includes a first member carrying a detent and a second member defining a cooperating recess. The detent and the cooperating recess positively define a predetermined bevel angle setting.
It is an advantage of the present invention to combine the simplicity of a conventional bevel angle adjustment mechanism with a detent to provide a user with identification of or a stop for frequently used bevel angles. The adjustment mechanism of the present invention provides the user with the choice of using the detent to provide a positive stop at the selective common angle or to override the detent and move to another common angle or a slightly offset angle.
It is another object of the present invention to provide a bevel angle adjustment mechanism which can be slightly offset from common detented angles.
It is another objective of the present invention to provide a bevel angle adjustment mechanism which includes a reduced number of parts.